Regeneration of sulfided dolomite

Abstract

Dolomite which has been used to remove sulfur and/or sulfur-containing compounds from gases by chemical reactions therewith is regenerated by passing through the spent dolomite an oxidizing gas selected from oxygen, CO2 and H2O at temperatures between about 1500 DEG F. and the temperature at which the dolomite becomes unreactive.

We claim: 
     
       1. Method of regenerating calcined dolomite sulfided with sulfur from a gas stream for reuse as a desulfurizing medium comprising passing through the sulfided dolomite an oxidizing gas consisting essentially of steam and CO 2  in a volume ratio of about 5:1 to 1:5 and about 0.5% to about 20% oxygen at a temperature in the range of about 1500° F. up to the temperature in which the crystalline structure of the dolomite becomes permanently altered thereby rendering a major portion of the dolomite inaccessible to the reacting gases. 
     
     
       2. A method of desulfurizing fuel gas comprising: (a) passing said gas through a bed of calcined dolomite to remove sulfur-containing gases therefrom, thereby generating CaS in the dolomite, and   (b) regenerating the calcined dolomite by the method of claim 1.   
     
     
       3. Method of claim 1 in which the oxidizing gas is combusted fuel gas containing from about 0.5% to 7% oxygen. 
     
     
       4. Method of claim 1 in which the dolomite is divided into a plurality of beds in series and a hydrogen containing gas is introduced into at least one downstream bed containing CaS to catalyze the reduction of SO 2  present in the gas. 
     
     
       5. Method of claim 1 in which the dolomite is divided into a plurality of beds in series and oxygen is introduced in at least one downstream bed at a concentration at which CaS is converted to CaO and SO 2  in preference to CaSO 4 . 
     
     
       6. Method of claim 5 followed by converting the SO 2  of the product gas into sulfuric acid. 
     
     
       7. Method of claim 4 in which water is injected into at least one bed of dolomite to cool it. 
     
     
       8. Method of regenerating calcined dolomite sulfided with sulfur from a gas stream for reuse as a desulfurizing medium comprising passing an oxidizing gas consisting essentially of CO 2  and steam in a ratio of from about 5:1 to about 1:5 in combination with about 0.5% to about 7.0% oxygen at a temperature between about 1500° F. and the temperature in which the crystalline structure of the dolomite becomes permanently altered thereby rendering a major portion of the dolomite inaccessible to the reacting gases through a plurality of beds of the dolomite in series, injecting oxygen into at least one downstream bed to maintain the concentration of oxygen therein up to 7%, and recovering a product gas containing at least 31/2% SO 2 . 
     
     
       9. Method of claim 8 including the additional step of converting the SO 2  in the product to sulfuric acid. 
     
     
       10. Method of claim 8 in which the oxidizing gas is passed through the plurality of beds of dolomite at a temperature in the range of 1500° to 2200° F. 
     
     
       11. Method of claim 8 in which a reducing gas is introduced into at least one downstream bed containing CaS to catalyze the reduction of SO 2  in the gas. 
     
     
       12. Method of claim 8 in which the gas passing through the plurality of beds is cooled prior to entering at least one of said beds.